The Supreme Court (search) gave police broader search powers Monday during traffic stops, ruling that drug-sniffing dogs can be used to check out motorists even if officers have no reason to suspect they may be carrying narcotics.

In a 6-2 decision, the court sided with Illinois police who stopped Roy Caballes (search) in 1998 along Interstate 80 for driving 6 miles over the speed limit. Although Caballes lawfully produced his driver's license, troopers brought over a drug dog after Caballes seemed nervous.

Caballes argued the Fourth Amendment (search) protects motorists from searches such as dog sniffing, but Justice John Paul Stevens disagreed, reasoning that the privacy intrusion was minimal.

"The dog sniff was performed on the exterior of respondent's car while he was lawfully seized for a traffic violation. Any intrusion on respondent's privacy expectations does not rise to the level of a constitutionally cognizable infringement," Stevens wrote.

Read the opinion by clicking here (Findlaw).

In a dissent, Justice Ruth Bader Ginsburg bemoaned what she called the broadening of police search powers, saying the use of drug dogs will make routine traffic stops more "adversarial." She was joined in her dissent in part by Justice David H. Souter.

"Injecting such animal into a routine traffic stop changes the character of the encounter between the police and the motorist. The stop becomes broader, more adversarial and (in at least some cases) longer," she wrote.

Chief Justice William H. Rehnquist did not participate in consideration of the case.

The case is another in a line of Supreme Court cases involving the Constitution's ban on unreasonable searches or seizures.

But civil liberties advocates have argued that allowing greater police powers in this case would be more troubling. That's because police often use traffic stops as a pretext to question motorists about suspected illegal activity for which they have no proof.

In Caballes' case, he was pulled over for driving 71 mph on a stretch of Interstate 80 with a 65 mph limit. The state trooper noticed air freshener in the car and asked for permission to search Caballes' trunk. Caballes refused, but officers searched it later anyway after the dog indicated there were drugs in the trunk.

The troopers subsequently found $250,000 worth of marijuana, a find that Caballes argued was unjustified because they had no reason to suspect he had drugs. His conviction was later thrown out by the Illinois Supreme Court, a ruling that the U.S. Supreme Court reversed.

The case is Illinois v. Caballes, 03-923.